Manually adjustable warning buzzer



Oct. 6, 1979 R. HAYDEN 3,533,103

MANUALLY ADJUSTABLE WARNING BUZZER Filed July 10, 1969 INVENTOR. -l i RODNEY HAYDEN "\K "35 .1) BY ATTORNEY United States Patent O 3,533,103 MANUALLY ADJUSTABLE WARNING BUZZER Rodney Hayden, Stoney Creek, Ontario, Canada, as-

signor to United-Carr Incorporated, Boston, Mass, a corporation of Delaware Filed July 10, 1969, Ser. No. 840,662 Claims priority, application Canada, Feb. 17, 1969, 043,084 Int. Cl. G08b 3/10 US. Cl. 340384 1 Claim ABSTRACT OF THE DISCLOSURE This is a buzzer using a one-piece armature which is tunable by manually manipulating the arm of the armature against a leaf spring.

BACKGROUND OF THE INVENTION In the manufacture of electric buzzers a consistent sound frequency of a large number of buzzers produced has been impossible to achieve heretofore without resorting to expensive characteristics of structure design and fabrication as well as extremes in inspection and quality control. This difiiculty is due to the fact that the spring biasing of the armature contributes along with the magnetic gap and contact gap, assuming all energizing coil structures and the mounting thereof is consistent.

In the automotive field there is a demand for an inexpensive buzzer of consistent sound, within a frequency range at a given normal temperature of say plus or minus ten cycles per second at a frequency of say four hundred and forty cycles per second. Such sound or note is capable of being tuned by car by an operator recording this invention with the tolerance suggested.

SUMMARY OF THE INVENTION This invention relates to an electric buzzer useful as a warning buzzer in automotive applications and adjustable by manual or other manipulation in production to establish a consistent buzzer note or frequency of sound.

It is an object of the invention to provide a buzzer structure which is tunable by simple manual manipulation in production to a predetermined frequency.

It is another object of the invention to provide an electric buzzer structure which is inexpensive and capable of being produced by inexpensive methods.

With the foregoing and other objects in view the invention generally concerns an adjustable sound frequency electric buzzer comprising: a buzzer winding supported by a core; a base supporting said core and winding; a movable armature having a free end and supported relative to said base and said core; means biasing said armature to move the latter away from said core to establish a magnetic gap; a rigid bendable standard rising from said base and having a limit flange overlying the free end of said armature; engageable contact members between said limit flange and said armature free end, said limit flange being manually bendable to effect normal engagement of said contact members and to position said armature to establish a predetermined magnetic gap; a bendable leaf spring extending toward and beyond the free end of said armature for sliding engagement by the latter at an angle of sliding friction therewith; and structure mounting said leaf spring relative to said base, said leaf spring being manually bendable to adjust the flexing return of said armature and the maximum separation of said contacts when said winding is energized thereby to control the frequency of the buzzer sound.

3,533,lfl3 Patented Oct. 6, 1970 ice BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings the adjustable sound frequency electric buzzer of the invention embodies a buzzer winding 10 wound on an iron core 11 between spool ends 12 and fixed to the insulate base 13 by rivet 14, being a projection of core 11. The buzzer of the invention is of particularly simple and inexpensive construction especially in the form of armature 15 provided. The armature 15 is preferably formed of a strip of springlike material containing iron, such as a high carbon steel suitably heat-treated to a predetermined hardness. The strip of C type configuration is fastened to base 13 between a support pad 16 and winding 10 by rivet 14 passing therethrough to leave the back portion 17 and upper armature arm 18 free under biasing spring tension of the material of the strip. The outward free terminal end 19 of upper armature arm 18 is positioned to define a desired magnetic gap 20 by bendably positioning the overlying limit flange 21 of contact standard 22. rising from base 13 and fastened to the latter by a rivet 2.3 through the standard base 24-.

Engageable contact members 25, 26 are preferably in the form of crosswise oriented half round contact alloy metal projection welded respectively to opposing surfaces of said limit flange 21 and the free terminal end 19 of upper armature arm 18.

The normally closed position of the contact members 25, 26 determines the magnetic gap 20 but the inherent tension of the material of the armature biasing its outward pressure effecting engagement of the contacts cannot be precisely the same in each production item of a series produced. Accordingly even adjustment of a series of such buzzers to provide the same magnetic gap will not provide substantially the same buzzer sound frequency or note.

The C form of the armature 15 may be modified to provide a square or upright back 17a as shown in FIG. 2 giving some further control of biasing tension. Such improvement still does not achieve the sound quality control necessary.

The invention provides a bendable leaf spring 27, preferably formed of a spring brass or spring bronze strip of material extending by its free end 28 toward and beyond the outward free edge or end 29 of free terminal end 19 of upper armature arm 18 for engagement by the latter at a suitable angle A of sliding friction (preferably less than about 45 degrees). Such structure in the form of armature upright 30 has spot welded thereto the fixed end portion 31 of leaf spring 27 to support same relative to the base 13.

Leaf spring 27 is adjustable manually in conjunction with adjustment of gap 20 in the manner indicated in FIG. 4 wherein the thumb 32 and first finger 33 of the right hand may engage limit flange 21 and base 13 while the first finger 34 and thumb 35 of the left hand engage the base 13 and leaf spring 27. A standard buzzer note within the hearing of the operator so gripping the buzzer of the invention while the latter is energized to provide a buzzing sound enables the operator to so manipulate and position limit flange 21 and adjusts simultaneously by bending the biasing pressure of leaf spring 27 that a similar note is easily achieved on a production basis.

In FIG. 3 are shown the two operative positions of the leaf spring and armature end 29. It is not essential that these members be in engagement in the normal position of contact engagement depending upon the spring force of the armature material and the frequency of the note required. The use of the leaf spring as shown also enables advantage to be obtained from some reflex action of the armature in the region of magnetic gap 20.

I claim:

1. An adjustable sound frequency electric buzzer comprising: a buzzer winding supported by a core; a base supporting said core and winding; a movable armature having a free end and supported relative to said base and said core; means biasing said armature to move the latter away from said core to establish a magnetic gap; a rigid bendable standard rising from said base and having a limit flange overlying the free end of said armature; engageable contact members between said limit flange and said armature free end, said limit flange being manually bendable to effect normal engagement of said contact members and to position said armature to establish a predetermined magnetic gap; a bendable leaf spring extending toward and beyond the free end of said armature for sliding engagement by the latter at an angle of sliding friction therewith; and structure mounting said leaf spring relative to said base, said leaf spring being manually bendable to adjust the flexing return of said armature and the maximum separation of said contacts when said winding is energized thereby to control the frequency of the buzzer sound.

References Cited UNITED STATES PATENTS 2,180,881 11/1939 Rostron 340384 HAROLD I. PITTS, Primary Examiner US. Cl. X.R. 

